1826 - Santa Fe Trail opened from Independence, MO to Santa Fe, NM: passe through Arapaho territory and brings increased disturbance

1831 - Bent's Fort established along the Arkansas River - becomes a major center of trading between Arapahos and Whites

1832 - Fort Laramie established in eastern Wyoming - becomes a second major trading center for the Arapahos. The two forts led to increasing separation of the Tribe into Northern and Southern Arapahos

1840 - Peace is established between Arapaho, Cheyenne, Comanch, Kiowa and Plains Apache in the southern plains - thus opening up the area to increased penetration by outsiders

1843 - Oregon Trail opens - major route through northern Arapaho territory

1849 - Gold Rush in California brings increased travel on trails across the Plains, along with epidemics

1851 - Fort Laramie Treaty establishes Arapaho territory as officially bounded by Platte River on north, Arkansas on south, continental divide on west, and western Kansas and Nebraska on the east